Conventional IC piston engines are made in a variety of cylinder configurations. For automotive engines, these include in-line, horizontally opposed and V-type configuration. Particularly with each automotive engine configurations, the engine is sized in volumetric capacity to enable desired maximum speed and acceleration requirements. However the engine size generally means that at low load conditions, and during deceleration and braking periods, which together form a major part of the operating time for the engine, fuel consumption is high because the engine needs to be throttled and operates at a much reduced overall efficiency.
Many attempts have been made to reduce the capacity of IC engines during low load conditions by one or both of variable stroke mechanisms and cutting off fuel to some of the cylinders. However, most of these attempts have not been successful or effective. In the case of shutting off fuel to some of the cylinders, there has been some improvements but, because the piston of each of the cylinders to which fuel is shut off is still moving and therefore contributing to overall friction levels, maximum benefits have not been derived.
In our International patent application WO2004/061270 and corresponding U.S. Pat. No. 7,174,863, there is disclosed a mechanism for internal combustion engines, and engines having the mechanism, which enables the stroke of at least one piston to be varied between extremes. In some instances, the stroke is able to be reduced to zero. Thus, when the stroke is reduced to zero and the fuel supply is shut off, the piston concerned is immobilised and hence it does not contribute to overall friction levels. However, the mechanism of WO2004/061270 and U.S. Pat. No. 7,174,863 is limited in the range of engine configurations in which it can be used. Also, engine configurations in which the mechanism is able to be used occupy a relatively large volume.
The present invention is directed to providing a rocking mechanism for an IC engine which, in an engine in which it is provided, is able to be adapted for at least one of variation in piston stroke, piston de-activation and variation in compression ratio. Relative to the mechanism of WO2004/061270 and U.S. Pat. No. 7,174,863, the present invention seeks to provide a mechanism suitable for a wide range of engine configurations and which enables a more compact engine form.